Single valley Dirac fermions in zero-gap HgTe quantum wells

TL;DR

This paper reports the discovery of a two-dimensional HgTe quantum well system exhibiting a single valley Dirac cone, with transport properties confirming Dirac fermion behavior and linear dispersion at the Dirac point.

Contribution

It demonstrates the existence of a single valley Dirac cone in HgTe quantum wells, advancing understanding of Dirac fermions in condensed matter systems.

Findings

Observation of quantized Hall plateaus indicating a single valley Dirac point

Linear dispersion of zero mode spin levels confirmed

Conductivity at the Dirac point matches Dirac fermion physics

Abstract

Dirac fermions have been studied intensively in condensed matter physics in recent years. Many theoretical predictions critically depend on the number of valleys where the Dirac fermions are realized. In this work, we report the discovery of a two dimensional system with a single valley Dirac cone. We study the transport properties of HgTe quantum wells grown at the critical thickness separating between the topologically trivial and the quantum spin Hall phases. At high magnetic fields, the quantized Hall plateaus demonstrate the presence of a single valley Dirac point in this system. In addition, we clearly observe the linear dispersion of the zero mode spin levels. Also the conductivity at the Dirac point and its temperature dependence can be understood from single valley Dirac fermion physics.